Batch rename - substitute repetitions

To try stop rename problems, I'd suggest that you play things safe in the future:

* Manually backup the originals first, or use the Batch Rename feature to copy the files to another directory

* Embed the original filenames in the XMP metadata so that they can be recovered if things go wrong (there is a preset to restore the preserved filename, the key is to preserve it first)

* Use the preview button to open up the window to double check all files, don't trust the quick preview at the bottom 100%

It is quicker to restore/recover backups than to try to rename a rename that had issues.

Yes, this sort of pattern matching is perfect for a regular expression based string substitution.

One of many possible regular expressions would be:

Find:

(\w+\.jpg)(.+)

Replace:

$1

If you had a mixture of file extensions (.jpg .tif .psd etc), then different code would be used rather than just the .jpg extension.

Some other valid regex find/replace combos include:

(\w+\.jpg|\w+\.psd)(.+)
$1

(.+)([A-Z][a-z0-9]*?\.\w*?$)
$2

(.+)([A-Z][a-z0-9]*?\.[^\.]+$)
$2

You can use one of the many sites such as regex101.com to explore the expressions as there are other valid choices, some more elegant than others, some more robust, some may be equivalent etc.

You can use what are called "regular expressions" to deal with complex patterns. Google the term for tutorials and sample code.